Cellulose and starch are two similar polymers, but the main difference between them is humans can eat starch but are not able to digest cellulose. The key difference is in the linkage of the glucose bonds. Cellulose has beta 1,4 linkage while starch has alpha 1,4 linkage. Cellulose occurs in nature as pure cellulose, lignin or hemicellulose. Whereas starch occurs in the form of amylopectin and amylose.

Starch

Starch is formed by the glycosidic linkage between α (1→4) and α (1→6) and it is a polymer of α-D glucose. C1-O-C4 looks like “V”.

Starch is not a single polymer. Starch is formed by the simple chained polyglucose, amylose and branched chain poly glucose, amylopectin.

Starch is the stored carbohydrate of cell, which is semi-soluble in water.

It is easily digestible and is used as food animals.

It is a non crystalline powder

Easily hydrolyzed.

Forms blue colour with iodine.

Cellulose

Cellulose is formed by β (1→4) glycosidic linkage and it is a polymer of β-D glucose C1-O-C4 looks like “A”-“V”-“A” alternatively.

Cellulose is a simple chain polyglucose.

Cellulose is the structural element which forms plant body and fibers. It is totally insoluble in water.

It is not digestible and so is not eaten a food. It is used in producing cloth, furniture etc.